DESCRIPTION: (Applicant's Abstract) Methamphetamine (MA) dependence is expanding rapidly in the United States, recapitulating early phases of epidemic spread in the 1950's and 1960's. Beyond the morbidity and mortality directly associated with addictive disease, MA is of particular concern in light of the HIV epidemic because it is often administered intravenously and it often increases libido. This confluence of sexual and injection drug use (IDU) risk factors has led to high HIV seroprevalence in MA using populations. Despite the rapid increase in MA dependence, little is known of its natural history and the relative contributions of sexual and IDU behaviors to the risk of HIV transmission. In a longitudinal study of MA dependence, we will use a comprehensive battery of assessments to identify predictors of high risk behaviors; the relative contributions of various sexual and IDU factors to HIV seropositivity; rates of HIV seroconversion; changes in risk behaviors and MA use following drug treatment; and the prevalence and stability of psychiatric comorbidity. Subjects will be recruited from the largely homosexual outpatient population at Haight Ashbury Detox in San Francisco, from predominately heterosexual outpatient population at The Effort in Sacramento, and from out-of-treatment MA users in San Francisco and Sacramento.